This document discusses monitoring surface deformation in New Zealand caused by a large 2016 earthquake using optical and radar satellite data. It combines differential interferometry (DInSAR) using Synthetic Aperture Radar (SAR) data and offset tracking (OT) to map displacement. DInSAR showed line-of-sight movement while OT mapped movements in east-west and north-south directions. Combining these techniques provided a more complete picture of the complex surface deformation than either method alone. The analysis demonstrated the potential of using multiple earth observation tools to study earthquake impacts.

1. Monitoring surface deformation combining Optical and
Radar Sentinel data:
C.A.Tourlakidis, E.Kalamatianou-Dimitropoulou, P. Krassakis, I. Gougoustamos, A.Fylaktos
I. Parcharidis
The New Zealand case

2. On November 14, 2016, a large magnitude [Mw] 7.8 earthquake
struck the northeastern part of the south island of New Zealand.
• more than 20 mapped faults
• caused widespread crustal deformation
• more than 10,000 landslides in the complex topography of the affected
area
"MOST COMPLEX EARTHQUAKE EVER STUDIED”
(Jibson et al. 2018)

3. MOTIVATION
• Ground deformation caused by earthquakes is a common phenomenon affecting
human activities resulting hazards in building stock and infrastructure.
• The ring of fire is known to generate seismic activities frequently because of its
many convergent boundaries (Plate-inward-sliding).
• Earth Observation techniques are quite common tools in order to monitor
surface deformation in the last decades.

4. AIM
• Why? Very complex earthquake
• Where? New Zealand-Plate kinematics
• Consequence? Hazardous ground deformation and earthquake-triggered
landslides
• Hypothesis? Combining different Earth Observation techniques and data
enhance our results
Monitor ground deformation in complex case studies:

5. Since 90’s differential repeat-pass interferometry radar (DInSAR) based on SAR images
processing has proven an interesting tool for the measurement and observation of ground
deformation (Massonnet and Rabaute., 1993).
Significant difficulties are found when using this technique. These difficulties are related to:
• large variability of slope instabilities,
• failure geometries,
• size of unstable areas
• phase ambiguity
• signal decorrelation.
EARTH OBSERVATION

6. The rocks of New Zealand can be grouped into four elements
which correspond to specific tectonic cycles in the geological
record:
• Western Province (Paleozoic)
• Eastern Province (Paleozoic to Cretaceous)
• Younger sedimentary and volcanic cover rocks
(Cretaceous to Cenozoic).
• The oldest rocks in New Zealand are Cambrian (they
occur only along the western margin of the South Island).
Most of the basement in New Zealand is Mesozoic greywacke,
and occurs as schistose metagreywacke (Haast Schist) in large
parts of the South Island New Zealand.
Also has an unusually thick and complete section of Cenozoic
rocks, most of which are marine sedimentary rocks, including
limestone, siltstone, and sandstone.
GEOLOGY

7. GEODYNAMICS
It’s location is on the boundary between the Pacific and
Indian-Australian plates
Subduction zones:
• Beneath the North Island, Pacific plate moves
down beneath the Australian plate causing
volcano activity
• South of New Zealand the Australian plate is
forced below the Pacific plate
Within the South Island the plate margin is marked by
the Alpine Fault and here the plates rub past each other
horizontally
Its dynamic geological past has endowed New Zealand
with spectacular scenery and a wide variety of natural
resources

8. LANDSLIDES
The majority of the triggered
landslides were shallow- to
moderate-depth (1–10 meters),
highly disrupted falls and slides
in rock and debris from Lower
Cretaceous graywacke
sandstone in the Seaward
Kaikoura Range.
Deeper, more coherent
landslides in weak Upper
Cretaceous to Neogene
sedimentary rock also were
numerous in the gentler
topography south and inland
(west) of the Seaward Kaikoura
Range.
Except from landslides also
surface ruptures, seabed rising
up to 1,5 meter.
The main scarp and upper part of the Sea Front landslide

9. The landslide inventory for the 14
November 2016 Mw7.8 Kaikoura
earthquake as at 19 May 2017.The
active fault ruptures caused by the
earthquake are shown as red lines
(Dellow et al. 2017).
Dellow, S., Massey, C.I., McColl, S.T., Townsend, D.B., Villeneuve, M.
(2017) Landslides caused by the 14 November 2016 Kaikoura
earthquake, South Island, New Zealand Proc. 20th NZGS Geotechnical
Symposium.

10. Two main tools based on earth observation data are used to estimate ground
surface movements both using SAR products.
• DInSAR (Differential Interferometry) based on phase and amplitude of SAR
SLC scenes and
• Offset tracking (OT) using amplitude-based method GRD in the case of
Sentinel images.
METHODS

11. DATA
Master Image Slave Image:
November 3rd 2016 December 3rd 2016
Master Image Slave Image:
November 3rd 2016 December 3rd 2016
Offset tracking: 2 GRD images of Ascending acquisition
For DInSAR: 2 SLC images of Ascending acquisition

12. A. DInSAR (Differential
Inteferomeromentry SAR)
Interferometric SAR (InSAR)
exploits the phase difference
between two complex radar
SAR observations of the same
area, taken from slightly different
sensor positions, and extracts
distance information about the
Earth's terrain.
If the phase shift related to
topography is removed from the
interferograms, the difference
between the resulting products
will show surface deformation
patterns occurred between the
two acquisition dates.
DATA-METHOD
S1-SLC: 3 November 2016 & 3 December 2016

13. B. Offset tracking
The OT is a method to
estimate the movements on
earth surface using two SAR
images (master and slave) in
both slant range and azimuth
direction .The method is
based on cross-correlation on
a preselected high number of
GCPs (Ground Control
Points) in the two scenes
after their coregistration. OT
is capable of tracking
movement rates from tens of
centimeters to tens of
meters.
S1-GRD: 3 November 2016 & 3 December 2016
DATA-METHOD

14. Displacement Map generated in
SARPROZ*, showing LOS
displacement.
Data used: 2 SLC Sentinel 1A&B
C-band
IW Sub-swath: 2
Master date: November 3rd 2016
Slave date: December 3rd 2016
*SARPROZ developed by Dr. D. Perissin, Purdue University, West Lafayette, USA

15. Max displacement map using
OT (Offset Tracking)
Data used: 2 GRD Sentinel
1A&B images C-band
IW Sub-swath: 2
Area deformed more than
10m in EW-NS directions

16. Displacement map using OT
(Offset Tracking) and DInSAR
(Differential Interferogram)
Data used: 2 SLC & 2 GRD
Sentinel 1A&B images
C-band
IW Sub-swath: 2

17. Displacement map using OT
(Offset Tracking) and DInSAR
(Differential Interferogram)
Data used: 2 SLC & 2 GRD
Sentinel 1A&B images
C-band
IW Sub-swath: 2

18. CONCLUSIONS
• An attempt was done to use optical data, but the results were poor
• The products were synthesized, although represent different results
• DInSAR show LOS movement – OT show EW-NS results
• We can make safe conclusions by combining SAR data analysis with our knowledge about
the area’s kinematics
• Further research can be done, combining DInSAR & OT providing results in common scale.
Thank you